Andersons pediatric cardiology 563
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (113 KB, 3 trang )
tointheadultpopulation.
PacemakerFunctionandFollow-up
Abasicunderstandingofthepacemakersystemandthecontinuousinteractions
withtheintrinsicactionofthepatient'srhythmisnecessary.Knowingthetypeof
pacemaker,theprogrammedparameters,aswellastheunderlyingrhythmis
vitaltobeabletoaccuratelyinterprettheECGandinternalelectrograms.The
purposeofthisreviewistofamiliarizethereaderwiththepacemaker
nomenclatureandthevariouspacemakersystemsutilizedforsymptomaticor
irreversiblebradyarrhythmias.
Tostandardizeandfacilitatetheunderstandingofpacemakers,theNorth
AmericanSocietyofPacingandElectrophysiologyandtheBritishPacingand
ElectrophysiologyGroup(BPEG)developedtheNBGcodingsystem,last
revisedin2002.195Thisthree-tofive-lettercodingsystemdeterminesthe
pacemaker'sfunction.Thefirstletterindicatesthechamberorchamberspaced.
Abbreviationsarethefollowing:Aforatrium;Vforventricle;Dfordual,
meaningatriumandventricle;andO,whichindicatesthattherapiesaredisabled
orasynchronous.PositionIIindicatesthechamberthatwillbesensed,withthe
sameabbreviationsasalreadymentioned.Thethirdletterdescribestheresponse
toasensedevent.TheletterIindicatesthatthepacemakerwillinhibitasensed
eventorTthatapacingstimuluswastriggeredbyasensedevent,orDhaving
dualcapabilitiestobothinhibitortriggerinresponsetoasensedevent.Position
IVisarate-modulationmode.RatemodulationRutilizesanaccelerometerthat
respondstothepatient'sphysiologicneedandisbasedonparameterssuchas
motionorminuteventilation.PositionVindicatesthepresenceorabsenceof
multisitepacing.
Somecommonprogrammedmodestoreviewarethefollowing:
▪TheDDDorDDD(R)systemhastheabilitytopace
andsenseineitherandorbothchambers.Functions
includepacinginbothchambersorinhibitionof
pacingbyasensedeventintherespectivechamber
andatrioventricularcoordinatedpacing.
▪TheVVIorVVI(R)systemisaventriculardemand
pacingmode(Fig.22.35).Theventricleispacedand
sensed,andthepulsegeneratorinhibitspacingoutput
inresponsetoasensedventricularevent.
FIG.22.35 TracingofasingleVVIpacemakerwithventricular
captureandappropriateventricularsensing.Notethatwiththe
appropriatelysensedintrinsicventricularbeatthedeviceresetsthe
timerandthenextventricularpacedbeatoccursatthelowerrate
limit.
▪TheAAIorAAI(R)systemisanatrialdemand
pacingmode.Theatriumispacedandsensed,andthe
generatorinhibitspacingoutputinresponsetoa
sensedatrialevent.
▪TheVOOorDOOmodesareasynchronousinthat
thegeneratorwilldeliverapacingstimulusatafixed
ratewithouttheabilitytosenseanyintrinsicevent.
TimingCycles
Timingcyclesrepresentthebeat-to-beatbehaviorofimplantabledevicesin
responsetothepatient'sintrinsicrhythm(Fig.22.36A–B).Anunderstandingof
thebasicconceptsofpacemakertimingcyclesisfundamentalinoptimizingcare
ofthepatient'srhythm.Pacemakertimingcyclesconsistofallthepossible
